Under certain medical and obstetrical circumstances, the uterine cervix of a woman at or near term does not undergo appropriate preparatory changes, and labor needs to be induced. It has been determined that a prostaglandin, known as prostaglandin E2, may be introduced endocervically to assist in ripening an unfavorable cervix.
The Upjohn Company has recently begun marketing a syringe prefilled with a premeasured single dose of 0.5 mg dinoprostone in 2.5 ml gel (Prepidil R Gel), administered through a catheter having a 10 or 20 mm shield near its distal end for blocking the cervix. The insertion of the catheter is accomplished with the use of a speculum to visualize the position of the cervix.
Atad (U.S. Pat. No. 4,976,692) discloses a catheter for use in the induction of labor that has two balloons positioned at the distal end of the catheter and an aperture in the catheter between the balloons. The catheter is positioned with the aid of a speculum so that the more distal balloon lies within the uterus and beyond the cervix and so that the more proximal balloon lies within the vagina proximal to the cervix. The more distal balloon is then inflated with fluid via one of three ports at the proximal end of the catheter, thus forming a blockage at the distal end of the cervix. The more proximal balloon is then inflated with fluid via the second of the three ports, thus sealing off the cervix from the vaginal side. Since the aperture in the catheter lies between the balloons, material may be introduced through the third port, which leads to the aperture, and the material is retained in the cervical area. A potential drawback to this apparatus is that the first balloon must reside within the uterus against the amniotic sac, thus raising the possibility of fetal harm. An economic disadvantage is that the apparatus has a complex construction, in that the catheter contains three ports, each opening onto one of three noncommunicating lumina.